import java.util.Random;
import java.util.Scanner;

public class YanZh {

    public static void main(String[] args) {

        System.out.println("输入验证码位数");
        Scanner sc = new Scanner(System.in);
        int i = sc.nextInt();
        System.out.println(yanZH(i));
    }

    public static String yanZH(int i) {

        String temp = "";
        Random r = new Random();
        for (int j = 0; j < i; j++) {

            int p = r.nextInt(3 );
            switch(p) {
                case 0:
                    int k = r.nextInt(10);
                    temp += k;
                    break;
                case 1:
                    char a = (char) (r.nextInt(26) + 65);
                    temp += a;
                    break;
                case 2:

                    char b = (char) (r.nextInt(26) + 97);
                    temp += b;
                    break;
            }
        }
        return temp;
    }
}
